         :is-random-replacement
         (if use-child false true)))))
 
+

        string-tweak (fn [st]
                       (apply str (map (fn [c]
                                         (if (< (lrand) uniform-mutation-string-char-change-rate)
                                           (lrand-nth (concat ["\n" "\t"] 
                                                              (map (comp str char) (range 32 127))))
                                           c))
                                       st)))
        constant-mutator (fn [token]

        string-tweak (fn [st]
                       (apply str (map (fn [c]
                                         (if (< (lrand) uniform-mutation-string-char-change-rate)
                                           (lrand-nth (vec (concat ["\n" "\t"] 
                                                                   (map (comp str char) 
                                                                        (range 32 127)))))
                                           c))
                                       st)))
        instruction-mutator (fn [token]
